CN101936873A - Method for obtaining standard instantaneous CO2 flux of soil profile - Google Patents

Abstract

The invention discloses a standard instantaneous CO2 flux concept of a soil profile and an obtaining method thereof. The method comprises the following steps of: firstly, detecting CO2 concentration in certain soil layer depth by an infrared CO2 analyzer and carrying out hyperbolic equation fit on the change of the CO2 concentration along with detecting time by software to obtain parameters a and b; using acknowledged atmosphere CO2 concentration as reference Ct to be substituted into a hyperbolic equation and calculating corresponding time t<s>; solving a first-order derivative of the hyperbolic equation by Ct to the time t and substituting a t<s> value into a derivative calculation formula to obtain a standard CO2 concentration change rate parameter corresponding to the time; and finally, substituting the standard CO2 concentration change rate parameter into a flux calculation formula to obtain the standard instantaneous CO2 flux of the detected soil layer. The invention can be used for carrying out rapid detection on multiple groups of repeated tests, reduces errors caused by detecting time intervals among a plurality of repeated tests and improves the reliability of data.

Description

The instantaneous CO of a kind of soil profile standard 2The acquisition methods of flux

Technical field

The present invention relates to agricultural environment information detection technology field, particularly relate to the instantaneous CO of a kind of soil profile standard ₂The acquisition methods of flux.

Background technology

Soil profile CO ₂The accurate monitoring of flux is the important content of terrestrial ecosystems carbon cycle process study.Obtain the instantaneous CO of the certain soil layer of soil profile ₂The common method of flux generally is by CO in the corresponding soil layer of METHOD FOR CONTINUOUS DETERMINATION ₂Concentration is in the variation of minute, then according to the forward and backward CO of minute ₂The difference of concentration, or by adopting linear fit, CO in the unit's of calculating minute ₂The mean change speed of concentration, and then obtain the CO of corresponding soil layer ₂Amount of flux.As seen, the flux mean value in the just minute that calculates thus, but not instantaneous flux truly if this mean value is replaced instantaneous flux, will inevitably cause instantaneous CO ₂Underestimating of amount of flux.The soil flux mainly is subjected to the influence of environmental factor (soil moisture, water cut etc.) and biodyne (root system of plant, soil microbial activities etc.) etc., reflection be the combined action result of researcher's various factors when measuring.Because environmental baseline (temperature, humidity, CO when different researchers measure ₂Concentration etc.) etc. difference, the non-standard attitude measurement result of just different " under the condition " of reflection causes the result who is difficult to different researchers rationally to compare thus, has limited the development in this field.And can then can address this problem for a standard flux of different researcher's references if having.

In view of above present soil CO ₂These problems that exist during flux is measured, the present invention proposes the notion and the corresponding acquisition methods thereof of the instantaneous flux of standard, the instantaneous state of determination object when measuring in the hope of making amount of flux both can reflect, provide when the result compares between different researchers again one can reference the universal standard.Adopt this method, also can obtain the instantaneous CO of its corresponding standard at the different soil degree of depth ₂Amount of flux.Present related standards CO ₂The also rarely seen report of the content of flux aspect.

Summary of the invention

The object of the present invention is to provide a kind of energy conveniently, accurately obtain the instantaneous CO of soil profile different soil standard ₂The method of flux.

The instantaneous CO of a kind of soil profile standard ₂The acquisition methods of flux is characterized in that carrying out according to following step:

One, at first adopts infrared CO ₂Analyser is to the CO at certain soil depth place ₂Concentration is measured, and minute is 5min, and data acquiring frequency is 10s; Wherein said soil depth all can according to any soil depth of taking of researcher's needs;

Two, with software to CO ₂Concentration is carried out the Hyperbolic Equation match with the variation of minute, obtains parameter a, b; Wherein said Hyperbolic Equation expression formula is:

$C_t=C_0+\frac{a\&CenterDot;t}{b+t}---\left(1\right)$

Wherein, C _tBe instant CO ₂Concentration (μ LL ^-1), t is minute (s), C ₀CO during for t=0 ₂Concentration (μ LL ^-1); A, b are fitting parameter.

Three, the Atmospheric CO to generally acknowledge ₂Concentration is 360 (μ LL ^-1) be reference standard, with C _tBe 360 (μ LL ^-1) bring Hyperbolic Equation into, calculate time corresponding t _sValue.

$t_s=\frac{360-C_0}{a-360+{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="HSA00000210503700011.png,HSA00000210503700021.png"\; state="\{\{state\}\}">C</figure-callout>}}_0}\&CenterDot;b---\left(2\right)$

Four, with the Hyperbolic Equation in the step 2 (1) with C _tT asks first order derivative to the time, can get:

$C_t^{\&prime;}=\frac{a\&CenterDot;b}{{(b+t)}^2}---\left(3\right)$

With the t in the equation (2) _sValue is brought following formula (3) into, obtains corresponding standard C O of this moment ₂Concentration change rate parameter k _s

$k_s=\frac{a\&CenterDot;b}{{(b+t_b)}^2}---\left(4\right)$

Five, with k _sValue is brought flux computing formula (5) into, can obtain to measure the instantaneous CO of standard of soil layer ₂Flux, wherein CO ₂The flux computing formula is as follows:

$F_s={\mathrm{\&rho;}}_0\&CenterDot;k_s\&CenterDot;\frac{V}{A}\&CenterDot;---\left(5\right)$

In the formula (5), F _sBe standard C O ₂Flux (mgm ^-2S ^-1), ρ ₀Be CO under the standard state ₂Density (1.96gL ^-1), V is the volume (m of sampling air chamber ³), A is sampling air chamber floorage (m ²), k _sBe standard C O ₂Concentration change rate parameter (μ LL ^-1S ^-1).

Therefore, by to CO ₂Concentration is carried out hyperbolic fit with the relation that minute changes, and calculates C _tBe 360 (μ LL ^-1) time correspondence t _sValue is obtained corresponding standard C O of this moment again ₂Concentration change rate parameter k _s, can bring the instantaneous CO of standard that the flux computing formula obtains to measure soil layer into ₂Flux.Adopt this method, also can obtain the instantaneous CO of its corresponding standard at the different soil degree of depth ₂Amount of flux.

Advantage of the present invention:

1) this method proposes standard C O ₂The notion of flux and acquisition methods are for the contrast between different results of study provides normative reference.Instantaneous

2) this method can be calculated instantaneous flux, and the flux that can effectively avoid conventional computing method to bring is underestimated problem.

3) but this method original position is obtained soil profile CO ₂Amount of flux need not to use any container to collect, and is on-the-spot with getting with survey, easily and fast.

4) this method is to CO in the mensuration process ₂Concentration is abundanter with the fitting data amount that minute changes, and fitting result is more reliable.

5) this method can be carried out fast measuring to many groups revision test, has reduced the error of bringing at interval because of minute between a plurality of repetitions, has increased the reliability of data.

Description of drawings

Fig. 1 each soil layer CO for recording under the different weather condition ₂Concentration is with the situation of change of minute, promptly October 9,16 days and 24 days CO ₂Concentration is with the variation of minute,

Fig. 2 is different time sections CO on October 12 ₂Concentration is with the situation of change of minute.

Embodiment

The layout of sampled point: bury the simple and easy impinger of self-control in advance underground at experimental plot soil different depth (5,10,15 and 20cm).The soil air collector is made of the glass funnel of wrapping up in nylon wire outward and inertia plastic conduit (internal diameter 2mm), and plastic conduit one end inserts inverted glass funnel neck, and the connection place seals with paraffin, and the other end is drawn ground.Earlier with the earth boring auger punching, different depth soil layer impinger is buried underground by mutual dislocation when burying underground, and by former soil layer backfill boring.Treat to observe after reclaimed soil and surrounding soil environment reach unanimity.

CO ₂The mensuration of concentration: carry out the instantaneous CO of different soil standard in each 9:00～11:00 in the morning that measures day ₂The mensuration of flux.During mensuration with plastic conduit by rubber hose and LI-840 CO ₂Analyser (Li-COR company produces, the U.S.) probe connects, and smears paraffin with anti-gas-leak at interface.The mensuration that will begin in a minute after connecting, minute is 5min, the data recording frequency is 10s.

With SigmaPlot software to CO ₂The match of concentration and minute relation: according to the actual CO that records ₂Concentration adopts Hyperbolic Equation that it is carried out match with the Changing Pattern of minute, and its equation is seen formula (1), obtains parametric equation a, b; Then with Atmospheric CO ₂Concentration is 360 (μ LL ^-1) be reference, by formula (2) calculate C _tBe 360 (μ LL ^-1) time correspondence t _sValue, (4) formula of bringing into again calculate corresponding standard C O of this moment ₂Concentration change speed k _sAt last with k _sValue is brought the instantaneous CO of standard that the flux computing formula obtains the soil layer of measuring into ₂Flux.Adopt this method, can obtain the instantaneous CO of standard of the different soil degree of depth (5,10,15 and 20cm) respectively ₂Amount of flux.

Embodiment 1:

In order to prove implementation result of the present invention, (groove width 60cm in the soil box of glasshouse, degree of depth 30cm) arranges the soil air collector in advance, and in the florescence of cucumber growth, choose 3 days (October 9,16 days and 24 days) and in the morning every day 9:00～11:00 carry out soil 5,10,15 and 20cm degree of depth standard C O respectively ₂The mensuration of flux.Adopt LI-840 CO ₂Analysis-e/or determining CO ₂The variation of concentration, minute are 5min, and the data recording frequency is 10s.Measure the back and carry out CO with SigmaPlot software ₂The hyperbolic relation match of concentration and minute, basis of calculation CO then ₂The instantaneous CO of concentration change speed and standard ₂Amount of flux.And the flux during with standard flux of the present invention and t=0, and the amount of flux that conventional method obtains compares, result of calculation sees the following form 1.Table 1, Fig. 1 have shown that all the present invention is to CO in the minute ₂The match of concentration change is more reasonable, reliable.

Table 1 fitting result of the present invention and the instantaneous CO of different soils degree of depth standard that calculates ₂Amount of flux

As can be seen from Table 1, fitting correlation coefficient of the present invention apparently higher than the linear fitting of routine, therefore confirms that fitting result of the present invention is more credible all greater than 0.99 (n=30).Flux when standard flux result that the present invention is obtained and t=0, and the amount of flux that conventional method obtains compares, visible standard amount of flux is apparently higher than other two kinds of results.For the analysis showed that of flux result between different soil, standard flux representation can effectively reduce contrast difference between soil layer than other two kinds of method for expressing.Flux as 5cm on the 10.9th and 20cm soil layer compares, and the former is on the low side 35% than the latter when representing with the standard flux, and the flux that flux or conventional method obtain during with t=0 represents then to be respectively 37% and 68%.

In addition, the relationship analysis of standard amount of flux and corresponding soils temperature shows in the table 1, and there is significant correlationship in the two, and (r=0.68, n=12), this also is corresponding to existing research conclusion, also further confirms reliability of the present invention simultaneously.

Embodiment 2:

For further proof implementation result of the present invention, in the test of plantation cucumber, carry out the different periods in one day (the instantaneous CO of standard of soil 5cm, 10cm, 15cm and the 20cm degree of depth of 7:00～17:00) ₂Flux is measured.Adopt LI-840 CO ₂Analysis-e/or determining CO ₂The variation of concentration, minute are 5min, and the data recording frequency is 10s.Carry out CO after the mensuration ₂The hyperbolic relation match of concentration and minute, basis of calculation CO then ₂The instantaneous CO of concentration change speed and standard ₂Amount of flux.And the flux during with standard flux of the present invention and t=0, and the amount of flux that conventional method obtains compares, and the results are shown in following table 2.Table 2 and Fig. 2 show that further the present invention is applicable to the mensuration of any period in one day too.

The instantaneous CO of different period soil 10cm degree of depth standards in table 2 the present invention calculate a day ₂Amount of flux

Can show further that from the result of table 2 the present invention is applicable to any period in one day, its fitting correlation coefficient is all greater than 0.99 (the n value is 30), apparently higher than the linear fitting of routine.Flux when standard flux of the present invention that the different periods are obtained and t=0, and the amount of flux that conventional method obtains compares, as seen the standard amount of flux is also apparently higher than other two kinds of results, and represents can effectively reduce contrast difference between soil layer than other two kinds of method for expressing with the standard flux.The relationship analysis of standard amount of flux and corresponding soils temperature shows in the table 2, the diurnal variation of amount of flux and the diurnal variation of temperature have consistance to a certain degree, correlationship reaches the level of signifiance, and (r=0.47, n=22), this has also further confirmed the reliability that result of the present invention is suitable for.

Claims (1)

1. instantaneous CO of soil profile standard ₂The acquisition methods of flux is characterized in that comprising following process: one, at first adopt infrared CO ₂Analyser is to the CO at certain soil depth place ₂Concentration is measured, and minute is 5min, and data acquiring frequency is 10s, and wherein said soil depth all can according to any soil depth of taking of researcher's needs;

Two, to CO ₂Concentration is carried out the Hyperbolic Equation match with the variation of minute, obtains parameter a, b; Wherein said Hyperbolic Equation expression formula is:

$C_t=C_0+\frac{a\&CenterDot;t}{b+t}---\left(1\right)$

Wherein, C _tBe instant CO ₂Concentration (μ LL ^-1), t is minute (s), C ₀CO during for t=0 ₂Concentration (μ LL ^-1); A, b are fitting parameter.

Three, the Atmospheric CO to generally acknowledge ₂Concentration is 360 (μ LL ^-1) be reference standard, be 360 (μ LL with Ct ^-1) bring Hyperbolic Equation into, calculate time corresponding t _sValue.

$t_s=\frac{360-C_0}{a-360+C_0}\&CenterDot;b---\left(2\right)$

Four, with the Hyperbolic Equation in the step 2 (1) with C _tT asks first order derivative to the time, can get:

$C_t^{\&prime;}=\frac{a\&CenterDot;b}{{(b+t)}^2}---\left(3\right)$

With the t in the equation (2) _sValue is brought following formula (3) into, obtains corresponding standard C O of this moment ₂Concentration change rate parameter k _s

$k_s=\frac{a\&CenterDot;b}{{(b+t_b)}^2}---\left(4\right)$

Five, with k _sValue is brought flux computing formula (5) into, can obtain to measure the instantaneous CO of standard of soil layer ₂Flux, wherein CO ₂The flux computing formula is as follows:

$F_s={\mathrm{\&rho;}}_0\&CenterDot;k_s\&CenterDot;\frac{V}{A}\&CenterDot;---\left(5\right)$

In the formula (5), F _sBe standard C O ₂Flux (mgm ^-2S ^-1), ρ ₀Be CO under the standard state ₂Density (1.96gL ^-1), V is the volume (m of sampling air chamber ³), A is sampling air chamber floorage (m ²), k _sBe standard C O ₂Concentration change rate parameter (μ LL ^-1S ^-1).

Images